TW201307588A - Highly bendable cu-co-si alloy wire - Google Patents

Abstract

The present invention relates to a Cu-Co-Si alloy wire demonstrating improved bendability during notching while maintaining strength and electroconductivity. This highly bendable Cu-Co-Si alloy wire contains 0.5-3.0 wt% of Co, 0.1-1.0 wt% of Si, and copper and inevitable impurities constituting the balance. Even in the surface layer and the central region, the maximum value of the X-ray random intensity ratio on the {200} pole figure is 3.0-15.0 in a range where the angle (a) around an axis perpendicular to the axis of rotation of a diffraction goniometer specified by the Schulz method is 0-10 DEG . A cross section that is parallel both to the rolling direction and to the plate-thickness direction preferably has 20-200 inclusions/mm2, each of the inclusions having a particle diameter of 1-2 [mu]m. The alloy wire optionally contains a total of 0.005-2.5 wt% of one or more elements from Sn, Zn, Mg, Fe, Ti, Zr, Cr, Al, P, Mn, Ni, and Ag.

Description

Cu-Co-Si alloy strip with excellent bending workability

The present invention relates to a Cu-Co-Si alloy strip suitable as a material for connectors, terminals, relays, switches, and the like.

In recent years, with the miniaturization of electronic machines, electrical. The miniaturization of electronic components is developing. Moreover, good strength and electrical conductivity are required for copper alloys used in such parts.

In the automotive terminal, it is also miniaturized, and requires good strength and electrical conductivity for the copper alloy used. Further, the female terminal for the vehicle is subjected to a notch process called a notching process on the curved inner surface before the press bending process. This is processed in order to improve the shape accuracy after the press bending process. Along with the miniaturization of the product, in order to further improve the shape accuracy of the terminal, there is a tendency that the dent process becomes deep. Therefore, in addition to good strength and electrical conductivity, a copper alloy used for a female terminal for a vehicle is required to have good bending workability.

According to this requirement, a precipitation-strengthened copper alloy such as a Carson alloy having high strength and electrical conductivity is used in place of the solid solution-strengthened copper alloy such as phosphor bronze or brass, and this demand is increasing. Among the Carson alloys, Cu-Co-Si alloys are alloy systems with relatively high strength and high electrical conductivity. The strengthening mechanism is due to the precipitation of Co-Si intermetallic compound particles in the matrix of Cu. The strength and electrical conductivity are improved.

In general, strength and bending workability are opposite, and it is expected to maintain high strength and improve bending processing even in Cu-Co-Si alloys. Sex.

A method for improving the bending workability of a Cu-Ni-Si alloy which is one of the Carson alloys is a method for controlling the crystal orientation described in Patent Documents 1 to 3. Patent Document 1 improves bending workability by making the {001}<100> area ratio of the EBSP analysis measurement result 50% or more; Patent Document 2, the {001}<100> area ratio by EBSP analysis measurement result 50% or more and no lamellar boundary to improve bending workability; Patent Document 3, by making the {110}<112> area ratio of the measurement result of EBSP analysis to be 20% or less, and making {121}<111> The area ratio is 20% or less, and the area ratio of {001}<100> is set to 5 to 60% to improve the bending workability.

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2006-283059

[Patent Document 2] Japanese Laid-Open Patent Publication No. 2006-152392

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2011-017072

However, in these methods, if the bending process is performed after the dent processing, cracks may occur in the bent portion, and in particular, if the kerf depth of the dent processing is long, a large crack is generated, and such a crack occurs. The improvement in bending workability is insufficient.

Accordingly, an object of the present invention is to improve the strength and electrical conductivity and to improve the bending workability of a Cu-Co-Si alloy, and in particular to improve the bending workability in the case of performing a dent process.

The present inventors conducted an effort to study the relationship between the crystal orientation of the Cu-Co-Si-based copper alloy and the bending workability, and as a result, it was found that the {200} pole figure is included in either of the surface layer and the central portion. 001}<100> azimuth area The X-ray random intensity is controlled to be greater than the maximum value to improve the bending workability, and in particular to improve the bending workability after the dent processing.

Further, it has been found that in order to control the X-ray random intensity ratio between the surface layer and the central portion, it is effective to cool at a specific speed after hot rolling to cause inclusions of a specific amount of particles having a particle diameter of 1 to 2 μm, and to adjust The strain rate of cold rolling after hot rolling.

That is, the present invention relates to the following invention.

(1) A Cu-Co-Si-based alloy strip excellent in bending workability, which contains 0.5 to 3.0% by mass of Co and 0.1 to 1.0% by mass of Si, and the balance is composed of copper and unavoidable impurities, and is on the surface layer. In any of the central parts, on the {200} pole figure, the axis rotation angle α perpendicular to the rotation axis of the diffraction goniometer specified by the Schultz method is in the range of 0 to 10°. The maximum value of the random intensity ratio of X-rays is 3.0~15.0.

(2) The Cu-Co-Si alloy strip according to (1), wherein the number of inclusions having a particle diameter of 1 to 2 μm parallel to the rolling direction and parallel to the thickness direction is 20 to 200/mm ² .

(3) The Cu-Co-Si alloy strip according to (1) or (2), containing 0.005 to 2.5% by mass of total of Sn, Zn, Mg, Fe, Ti, Zr, Cr, Al, P One or more of Mn, Ni, and Ag.

It is possible to obtain a Cu-Co-Si-based copper alloy which is excellent in bending workability even if it is subjected to dent processing on the curved inner surface before the press bending process.

(1) Co, Si concentration

Co and Si are precipitated as a Co-Si-based intermetallic compound by aging treatment. This compound increases the strength, and Co and Si dissolved in the Cu matrix are reduced by precipitation, so that the electrical conductivity is improved. However, if the Co concentration is less than 0.5% by mass (hereinafter referred to as %) and/or the Si concentration is less than 0.1%, the desired strength cannot be obtained. Conversely, if the Co concentration exceeds 3.0% and/or the Si concentration exceeds 1.0%, Hot workability is degraded.

(2) Other added elements

The addition of Sn, Zn, Mg, Fe, Ti, Zr, Cr, Al, P, Mn, Ni, and Ag contributes to an increase in strength. Further, Zn is effective for improving the heat-resistant peelability of Sn plating, and Mg is effective for improving stress relaxation characteristics, and Zr, Cr, and Mn are effective for improving hot workability. If the concentrations of Sn, Zn, Mg, Fe, Ti, Zr, Cr, Al, P, Mn, Ni, and Ag are less than 0.005% by total, the above-mentioned improvement effect cannot be obtained. Conversely, if it exceeds 2.5%, the conductivity is obtained. Significantly reduced and cannot be used as electrical. Electronic parts materials.

(3) X-ray random intensity ratio

Increasing the X-ray random intensity ratio maximal value of the {001}<100> azimuth region on the {200} pole figure is effective for improving the bending workability, especially the bending workability after the dent processing. Further, the X-ray random intensity ratio is increased together with the surface layer and the central portion, and is effective for improving the bending workability after the dent processing. In the present specification, the term "surface layer" means a portion having a depth of 1/6 from the front and back surfaces of the alloy strip to the center of the sheet thickness, and the "central portion" indicates a portion other than the surface layer. Furthermore, on the {200} pole figure, the {001}<100> orientation is an axis rotation angle α perpendicular to the rotation axis of the diffraction goniometer specified by the Shure method, and parallel to the rotation axis. The axis rotation angle β corresponds to α=0~10° and β=0~360°.

The present invention is measured in an X-ray diffractometer (RINT 2500 manufactured by RIGAKU Co., Ltd.) in the surface layer and the center portion, and it is found that α is in the range of 0 to 10° on the {200} pole figure (refer to When the maximum value of the X-ray random intensity ratio of Fig. 1) is 3.0 or more, the bending workability is good. In the surface layer and/or the center portion, if the maximum value is less than 3.0, the bending workability is deteriorated. On the other hand, the maximum value is currently difficult to exceed 15.0. Therefore, the upper limit of the maximum value is set to 15.0. Preferably, the maximum value of any of the surface layer and the central portion is 5.0 or more.

The reason for achieving excellent bending fracture resistance by adjusting the random intensity of X-rays in the {001}<100> orientation is not clear, but it is considered that the {001}<100> orientation system is more resistant to plasticity than other orientations. The orientation of the introduction of the shear band at the time of deformation is difficult to cause breakage during bending. However, the invention is not limited by the above theory. The range of α and β described above is determined by considering the peak position of the X-ray intensity ratio due to processing, heat treatment conditions, measurement errors, and the like.

The depth of the slit generated by the dent processing which is usually performed in the terminal manufacturing step can be deep to the center portion of the thickness. Even if only the maximum value of the X-ray random intensity ratio of the surface layer of the thickness is increased, a micro crack is generated in the central portion of the thickness during the dent processing, and it is propagated to the bending process after the dent processing. The surface layer is cracked. Therefore, the maximum value of the X-ray random intensity ratio is increased in either of the surface layer and the central portion to adjust the crystal orientation, which is effective for improving the bending workability.

On the other hand, Patent Documents 1 to 3 measure the crystal orientation of the surface. The controller does not control the crystal orientation of the center portion (requests 1 of Patent Documents 1 to 3). Therefore, the bending process after the dent processing is performed at the center portion of the thickness of the sheet to cause microcracking, and the bending workability is deteriorated.

(4) inclusions

In the present invention, the term "inclusion" means a concept including a generally coarse crystal formed by a solidification process at the time of casting and an oxide, a sulfide, or the like which is produced by a reaction in a melt at the time of melting. And further comprising a precipitate formed by a precipitation reaction in a solid phase matrix after a solidification process at the time of casting, that is, a cooling process after solidification, a hot rolling, and a cooling process after the solution treatment. Contains particles observed in the matrix by SEM observation of the copper alloy (so-called second phase particles).

The "particle diameter of inclusions" means the diameter of the smallest circle including the inclusions measured by SEM observation. The term "the number of inclusions" means a particle which is different from the parent phase in a plurality of portions in a cross section parallel to the rolling direction of the material and parallel to the thickness direction of the material, and observed by SEM after etching. The average number of squares in mm.

As described above, the inclusions of the present invention also contain particles formed in the step after hot rolling, but mainly contribute to the desired function of the present invention by inclusions of a specific size which are present after hot rolling.

Specifically, if the inclusions having a particle diameter of 1 to 2 μm in the calender parallel cross section after hot rolling are present in the range of 20 to 200/mm ² , the X-ray random intensity ratio of the surface layer and the central portion is maximal. It is 3.0 or more. If it is outside the range of 20 to 200 / mm ² , the maximum value of the X-ray intensity ratio is less than 3.0, and the bending workability is deteriorated.

Further, the number of inclusions having a particle diameter of more than 1 μm after hot rolling is substantially the same as the number of final products obtained by a manufacturing step of a Cu-Co-Si alloy including cold rolling, solution treatment, and aging treatment. .

Specifically, if the material having a uniform particle diameter of 1 to 2 μm is uniformly rolled in the thickness direction after hot rolling, the processing strain will concentrate on the periphery of the inclusion, so the strain will be in the thickness of the plate. The direction is evenly distributed. When the material is subjected to a solution treatment, the crystal grains of the {001}<100> orientation are uniformly recrystallized in the thickness direction, so that the X-ray intensity ratio within the above range can be obtained.

However, the reason for the bending process cracking is considered to be that if the precipitated reinforced copper alloy has coarse inclusions having a particle diameter of 1 to 2 μm after hot rolling, there is a fine second phase in the subsequent solution treatment step. The particles cannot be analyzed and cannot achieve the target's strengthening effect, and will become the starting point of the fracture during bending. Therefore, in the production step of the precipitation-strengthened copper alloy, it is sufficiently heated in the hot rolling so as not to cause inclusions after hot rolling, and is rapidly cooled by water cooling after hot rolling (for example, Patent Document 1) 0026", Patent Document 2 "0062", Patent Document 3 "0030").

None of the above Patent Documents 1 to 3 pay attention to the conditions of the hot rolling step, and the crystal orientation of the calendering surface is adjusted only by controlling the degree of processing of the calendering or the solution treatment conditions. However, in the cold rolling after hot rolling, if the strain rate is not controlled, the processing strain generated in the surface layer and the center portion will be different, and thus the crystal orientation of the surface layer and the center portion will be different. Further, in the solid solution treatment, the heat received by the surface layer and the central portion is not the same, and the central portion where the influence of heat is less is unable to achieve the target crystal orientation. Therefore, in these patents According to the manufacturing method, the crystal orientation of the central portion cannot be controlled, and the maximum value of the X-ray random intensity ratio including the {001}<100> azimuth region is not increased at the central portion.

(5) Manufacturing steps

In the manufacturing process of the present invention, first, an atmospheric melting furnace is used, and a raw material such as electrolytic copper, Co, or Si is melted under charcoal coating to obtain a desired composition melt. The melt is then cast into an ingot. Thereafter, hot rolling is performed, and cold rolling, solution treatment (10 to 300 seconds at 700 to 1000 ° C), aging treatment (2 to 20 hours at 400 to 600 ° C), and final cold rolling (processing degree 5) are performed. ~40%). Relaxation annealing can also be performed after the final cold rolling. The relaxation annealing is usually carried out at 250 to 600 ° C for 5 to 300 seconds in an inert gas atmosphere such as Ar. Further, it is also possible to carry out cold rolling between the solution treatment treatment and the aging treatment to increase the strength. Further, the final cold rolling and aging treatment may be sequentially performed after the solution treatment, and the order of the steps may be replaced. If it is used in the manufacturing step of the Cu-Co-Si alloy and is within the conditions of the usual solution treatment, aging treatment and final cold rolling as exemplified above, the hot rolling and the subsequent cooling are carried out under the following conditions. The calendered material recrystallizes the grain of the target orientation in the surface layer and the central portion after solution treatment, and the structure of the crystal orientation after aging treatment and final cold rolling does not change substantially.

Hereinafter, the production conditions of important steps in the method for producing an alloy strip of the present invention will be described in detail.

(A) Hot rolling

The ingot is heated at 800 to 1,000 ° C for 1 to 20 hours and homogenized and annealed, followed by rolling. After the calendering, the cooling rate during the temperature reduction of the material from 600 ° C to 300 ° C is preferably from 10 to 100 ° C / min, more preferably from 20 to 80 ° C / min. If the cooling rate is outside the above range, the inclusions having a particle diameter of 1 to 2 μm may be outside the range of 20 to 200/mm ² . That is, if the cooling rate is fast, the inclusions having a particle diameter of 1 to 2 μm may be less than 20/mm ² , and in the next cold rolling step, uniform strain may not be generated in the thickness direction, and if the cooling rate is slow, the particle diameter is 1~ The inclusions of 2 μm will exceed 200/mm ² , and in the next cold rolling step, uniform strain will not occur in the thickness direction, and the bending property will be lowered.

(B) Cold rolling after hot rolling

The strain rate of the cold calendering after hot rolling is preferably from 1 × 10 ^-6 to 1 × 10 ^-4 /s, more preferably from 5 × 10 ^-6 to 8.0 × 10 ^-5 / s. The "strain rate" of the present invention is specified as the calendering speed / roll contact arc length. When the strain rate is less than 1 × 10 ^-6 /s, the X-ray intensity ratio of the obtained material is 3.0 or more in the surface layer, but is less than 3.0 in the center portion. On the other hand, when it exceeds 1 × 10 ^-4 /s, the maximum value of the X-ray intensity ratio of the obtained material is 3.0 or more in the center portion, but it is not preferable because the surface layer is less than 3.0.

[Examples]

The embodiments of the present invention and the comparative examples are shown below, but the examples are provided to better understand the present invention and its advantages, and are not intended to limit the invention.

The electrolytic copper was melted by 2.50 Kg in a high-frequency melting furnace under an argon atmosphere with an inner diameter of 110 mm and a depth of 230 mm of alumina or magnesia. Add elements other than copper according to the composition of Table 1, and adjust the melt temperature to 1300. After °C, the molten metal was cast into a 30×60×120 mm ingot using a mold (material: cast iron), and a copper alloy strip was produced by the following procedure.

(Step 1) After heating at 950 ° C for 3 hours, the film was hot rolled to a thickness of 10 mm, and the material temperature was changed from 600 ° C to 300 ° C as shown in Table 1.

(Step 2) The rust scale on the surface of the hot rolled sheet is ground and removed by a grinder.

(Step 3) Cold rolling to a plate thickness of 0.180 mm at the strain rate shown in Table 1. The strain rate is determined by the calendering speed/roller contact arc length.

(Step 4) Heating at 1000 ° C for 10 seconds in the air, and quenching in water as a solution treatment.

(Step 5) Heating was carried out for 5 hours at 550 ° C in an Ar atmosphere using an electric furnace as an aging treatment.

(Step 6) Final cold rolling is performed until the sheet thickness is 0.15 mm.

(Step 7) As a relaxation annealing, it was heated at 400 ° C in an Ar atmosphere for 10 seconds.

The samples thus prepared were evaluated for the following characteristics.

(1) inclusions

After hot rolling, the cross-sectional structure parallel to the rolling direction and parallel to the thickness direction was exposed by etching (water-NH ₃ (40 vol%)-H ₂ O ₂ (0.6 vol%)), and FE was used. - SEM (XL30SFEG manufactured by FEI Corporation, Japan) observed a secondary image of 1 mm ² field of view at a magnification of 750 times. Thereafter, the particle diameter and the number of inclusions in the observation field of view were respectively determined using an image analyzer. Further, the inclusions of the product after the final step were also measured, and it was confirmed that the number of inclusions having a particle diameter of 1 to 2 μm after hot rolling did not largely change after the final step.

(2) X-ray random intensity ratio maximum value

The {200} pole measurement of each sample was carried out by a X-ray diffractometer (RINT2500, manufactured by RIGAKU Co., Ltd.) using a Co tube (Co X-ray tube) at a tube voltage of 30 kV and a tube current of 100 mA. And make a {200} pole figure. The X-ray intensity of the above range (α = 0 to 10 °, β = 0 to 360 °) was measured, and the copper powder as a standard sample measured in the same manner was calculated (Kantong Chemical Co., Ltd., trade name: copper ( The ratio of the X-ray intensity of the powder) 2N5) and the maximum value thereof. The X-ray random intensity ratio of the surface layer is the maximum value of the calendered surface, and the X-ray random intensity ratio at the central portion is measured by the spray etching of the ferric chloride solution to make the central portion of the plate thickness (plate thickness). 1/2 of the depth) exposed. Further, a solution of phosphoric acid 67% + sulfuric acid 10% + water was applied to the surface of the calendered surface by electrolytic polishing at 15 V for 60 seconds to expose the structure to water and then dried, and then the calendered surface was measured.

(3) 0.2% endurance and electrical conductivity

0.2% of the endurance was measured in accordance with JIS Z 2241 using a tensile tester. The so-called good strength of the present invention means that the 0.2% proof stress is in the range of 500 MPa to 950 MPa, preferably 600 to 950 MPa.

The conductivity was measured in accordance with JIS H 0505. The term "good conductivity" as used in the present invention means 50% IACS or more, preferably 60% IACS or more.

(4) Flexibility

Evaluation of the bending property, the implementation of the depth of 25, 50, 75 μm dent plus After the work (see FIG. 2A), the bending radius was 0 mm and the 90°W bending process was performed in the GoodWay direction in accordance with JIS H 3130 (see FIG. 2B). Further, the sample to which the indentation is attached in Fig. 2A is turned upside down in Fig. 2B to perform bending processing. The section of the bent portion parallel to the rolling direction and parallel to the sheet thickness direction (see FIG. 2C) was finished into a mirror surface by mechanical polishing and polishing, and the presence or absence of cracking was observed with an optical microscope (magnification: 50 times). The case where the fracture was not confirmed under the observation of the optical microscope was evaluated as ○, and the case where the fracture was confirmed was evaluated as ×.

In the present invention, "excellent bending workability" means that when the above evaluation is performed on a sample having a thickness of 0.15 mm, no breakage was observed even when the dent was processed at a depth of 50 μm.

The examples are shown in Table 1. Inventive Examples 1 to 17 were within a predetermined range, and even if the bending process was performed after the dent processing with a depth of 50 μm, no fracture was observed, and good bending workability was exhibited. Among them, Invention Examples 2, 3, 6 to 8, 11, 12, and 14 ensure excellent strength and electrical conductivity, and no fracture was observed even after bending processing was performed after dent processing having a depth of 75 μm at half the thickness of the sample.

In Comparative Example 1, since the concentrations of Co and Si were both low, the 0.2% proof stress was low. In Comparative Example 2, since the concentrations of Co and Si were both high, fracture occurred at the time of hot pressing. In Comparative Example 3, since the concentration of the added element other than Co and Si is high, the conductivity is low and it is not suitable as an electric. Electronic parts materials.

Comparative Example 4 is an example in which the number of inclusions is large due to the slow cooling rate of hot rolling. The maximum value of the X-ray random intensity ratio is less than 3.0 in the surface layer and the central portion, and the bending workability is poor. In contrast, Comparative Examples 5 and 6 are for hot pressing A prior art example in which water cooling is postponed. Since the cooling rate is fast, the number of inclusions is small, and the effect of uniform dispersion of the processing strain due to uniform distribution of inclusions cannot be obtained. Even if the strain rate of cold rolling is within an appropriate range, the random intensity of X-rays is greater than the maximum value. It is less than 3.0 in the surface layer and the center portion, and the bending workability is poor.

Comparative Examples 7 and 8 are examples in which the strain rate of cold rolling after hot rolling is fast. Although the maximum X-ray intensity ratio at the center is 3.0 or more, the surface portion is less than 3.0, and the bending workability is inferior even if the punching depth is 25 μm (1/6 of the thickness). On the contrary, Comparative Examples 9 and 10 are examples in which the strain rate of cold rolling after hot rolling is slow. Although the X-ray random intensity ratio of the surface layer is greater than 3.0, the central portion is less than 3.0. Although the fracture depth is 25 μm, no fracture occurs, but it is 50 μm (1/3 of the thickness). When a fracture occurs, the bending workability is poor.

2‧‧‧sample

3‧‧‧Deep processing depth

21‧‧‧Rolling direction

22‧‧‧ plate thickness direction

23‧‧‧Bending processing observation surface

Fig. 1 is a {200} pole figure showing a range in which the axis rotation angle α perpendicular to the rotation axis of the diffraction goniometer specified by the Shure method is 0 to 10° in the gray portion (in the center circle).

Figure 2A is a schematic illustration of the dent processing step. The arrows in the figure indicate the direction of pressure.

Figure 2B is a schematic illustration of a 90° W bending process step.

Fig. 2C is a schematic view showing the observation surface after the bending process.

Claims (3)

A Cu-Co-Si alloy strip excellent in bending workability, containing 0.5 to 3.0% by mass of Co and 0.1 to 1.0% by mass of Si, and the balance being composed of copper and unavoidable impurities, and being in the surface layer and the central portion. In either case, on the {200} pole figure, the X-ray random intensity ratio is extremely large in the range of 0 to 10° from the axis of rotation α of the angle of rotation of the goniometer specified by the Shure method. The values are all from 3.0 to 15.0. For example, in the Cu-Co-Si alloy strip according to item 1 of the patent application, wherein the number of inclusions having a particle diameter of 1 to 2 μm parallel to the rolling direction and parallel to the thickness direction is 20 to 200/mm. ² . The Cu-Co-Si alloy strip according to claim 1 or 2 contains Sn, Zn, Mg, Fe, Ti, Zr, Cr, Al, P, Mn in a total amount of 0.005 to 2.5% by mass. One or more of Ni and Ag.